Chair construction



'Marh4,19e9 l R, p. POPpE am 3,431,022

CHAIR CONSTRUCTION Filed may 29, 1967 v shet l of a March 4, 1969 R P, POPPE ET AL CHAIR CONSTRUCTION Sheet .2 of2 Filed May 29, 1967 ma ENS d United States Patent O 3,431,022 CHAIR CONSTRUCTION Robert P. Poppe and Donald E. McNally, Grand Rapids,

Mich., assignors to Steelcase, Inc., Grand Rapids, Mich.,

a corporation of Michigan Filed May 29, 1967, Ser. No. 641,780

U.S. Cl. 297-445 29 Claims Int. Cl. A47c 5/00, 7/.00, l/IZ, .Z1/00 ABSTRACT OF THE DISCLOSURE A chair construction having a relatively thin seat portion suspended along both of its side edges between a pair of horizontally extending rail portions forming a part of a frame arrangement, in which the side edges of the seat portion are ared to provide a dovetail and each of the rail portions have a dovetaled groove forward therein, such that the seat portion is attached to the rail portions by sliding engagement of such flared enlargements and grooves to form a dovetail joint, which then supports the seat portion in a sling suspension. Also, a support structure is provided which extends between the aforesaid rail portions to maintain a desired separation thereof when weight is placed upon the seat portion. The support structure is spaced beneath the seat portion for the most part, but has a support shoe at each end which is disposed immediately beneath and in contact with the underside of the seat portion immediately inwardly of the aforesaid dovetailed joint. Also, leg structures are provided for the chair which have portions lying laterally adjacent the rail portions and secured to the aforesaid support structure so as to clamp the rail portions between the leg structures and the end extremities ofthe support structure.

BACKGROUND In relatively recent times, a family of general-purpose or random-utility chairs has become very popular. In such chairs the seat portions and backrests are relatively thin curved or otherwise contoured members constructed of such materials as molded plastic, plastic-clad sheet metal, and the like. While these chairs are extremely functional by nature and useable in a wide variety of different situations, design esthetics has also played a major part in both their creation and their overall popularity, the thin and contoured seats and backrests giving these chairs a smart, clean, and contemporary or modern appearance.

The mounting and the support of the thin and often somewhat flexible backrest and seat portions of such chairs has always provided a challenging problem, in that many different approaches have been taken or attempted in order to provide the various degrees of support needed by these respective members and the required secure retention of edges and the like, while simultaneously providing for the freedom of suspension which is desired for these members, so that their inherent resiliency and at least modest flexibility can be used to its best advantage. A very basic and integral part of this area of concern is the exact nature of the frame which is designed for use in the particular chair construction, including the frame configuration and its construction as well.

SUMMARY OF THE INVENTION The present invention comprises an improvement in chair constructions of the aforementioned type and provides a new form of suspension for the backrest and the seat portion, particularly the latter, wherein such portion is mounted by means of a sling suspension in which it is subject almost exclusively to only tension forces when it is placed under a load, and in which the natural resilience of the seat portion remains uninhibited even though it is 3,431,022 Patented Mar. 4, 1969 ICC mounted in an extremely secure fashion. Furthermore, the basic frame assembly of the present chair construction has unique structural features rendering the frame extremely rigid and strong for great durability under even the most rigorous usage.

Basically, the present invention provides a chair construction wherein cooperative means along opposite edges of the seat portion and along each of a pair of horizontal rails forming a part of a frame assembly and lying adjacent each side of such seat portion form a dovetail joint between such rail portions and seat portion edges. The seat portion is assembled to the rail portions by relative sliding of such dovetail joints, and in use these joints sustain the weight placed upon the seat portion, such that the seat is placed in a sling suspension between the rails. Support means are provided beneath the seat portion for maintaining the mutual separation of the horizontal rails, but this support is placed beneath most of the seat portion so as not to interfere with the sling suspension thereof. Near each end extremity of the support means is formed a generally at or slightly convex support shoe or anvil element which extends upwardly to contact the seat portion along an area extending adjacent the dovetail and immediately inwardly thereof, to support the seat along this area and maintain the seat portion in tension by orienting it with respect to the dovetail to eliminate bending and shear forces.

DRAWINGS FIG. 1 is a lateral perspective view of the chair construction of the invention;

FIG. 2 is an enlarged front elevation of the backrest portion of the chair;

FIG. 3 is a further enlarged cross-sectional View taken through the plane IIIIII of FIG. 2;

FIG. 4 is an enlarged bottom plan view of the seat portion of the present chair;

FIG. 5 is a further enlarged sectional elevation taken through the plane V-V of FIG. 4;

FIG. 6 is a further enlarged sectional elevation taken through the plane VI--VI of FIG. 4;

FIG. 7 is a further enlarged sectional elevation taken through the plane VII-VII of FIG. 4; and

FIG. 8 is an enlarged sectional elevation taken through the plane VIII-VIII of FIG. 4.

PREFERRED EMBODIMENT As seen in FIG. 1, the chair construction 10 of the invention has a separate back or backrest portion 12 and seat portion 14, lboth of which are preferably contoured with a rsomewhat convex shape for greater comfort to the user. The backrest and seat are mounted on a frame assembly 16 which is preferably of diecast aluminum alloy and which includes a pair of generally L-shaped rails 18 and 20. These define a pair of generally horizontal rail portions 18a and 20a lying adjacent each lateral edge of the seat portion 14, from which the rails curve upwardly to lie adjacent each edge of the backrest 12. Also, the frame assembly includes a pair of chair leg structures 22 and 24, each comprising an inverted generally U-shaped structure including a pair of angularly-disposed legs interconnected by a portion located adjacent and immediately outward of the horizontal rail portions 18a and 20a, by which the legs are secured to the frame assembly.

The backrest portion 12 is seen in more detail in FIGS. 2 and 3. This includes a backrest panel designated 26 which directly supports the back of a person sitting in the chair, as well as the upper extremities of the rails 18 and 20, which extend generally vertically from the rail portions 18a and 20a adjacent the seat portion 14, noted previously. As indicated in FIG. 3, the backrest panel 26 is generally free and unsupported over most of its excursion, and is retained securely by attachment along its edges to rails 18 and 20. This attachment comprises a dovetail joint formed by an outwardly-flared end extremity 26a and 26b along each side of the backrest panel which ts into a complementary dovetail groove 19 and 21, respectively, formed in the two rails 18 and 20. Also, each end extremity of the -backrest panel 26 has a rear- -Wardly disposed outwardly-projecting V-shaped ridge 28 and 30, one side surface of which rests against and bears upon a correspondingly angled surface 32 and 34 formed on each of the rails 18 and 20, at the mouth or entrance of the aforesaid dovetail grooves 19 and 21. As will readily be understood, this feature helps to brace the dovetail joint along each side of the backrest panel and maintain the panel under tension, as opposed to shear or bending stresses, against the weight of a person leaning back in the chair.

As illustrated in FIGS. 1 and 2, the vertically-extending portions of the rails 18 and 20 do not extend completely to the top of the backrest panel 26, but instead terminate slightly beneath it. The top of the backrest panel 26 extends laterally outward at 25 and 27 to form projecting shoulders which cover the top ends of the rails 18 and 20 and abut against the sa-me to hold the backrest panel in the position illustrated in FIG. 2 and prevent downward relative sliding of the dovetail joint which joins each side of the backrest panel to the respective rails. The backrest panel itself is, like the seat portion 14, preferably made of a semirigid moldable plastic such as polypropylene, by which the particularly shaped ilared and angled edge extremities of this panel may readily be formed. While the vertically-extending portions of the rails 18 and 20 are preferably at least slightly vertically convergent, the backrest panel 26 may nonetheless be assembled to such rail portions by relative sliding of the dovetail joints which hold the backrest panel thereto, first by sliding one ilared edge 26a or 26b into its respective groove 19 or 21 in one of the rails, and then by sliding the other such flared end into the other such grooved rail.

The seat portion or panel 14, as seen in FIGS. 4, 5, 6, 7 and 8, is suspended between the horizontal portion 18a and 18b of rails 18 and 20 in a manner which is similar to that already described in connection with the backrest portion. That is, the side edges of the seat :portion 14 are each formed to have outwardly flaring enlargements forming a dovetail 36 (FIGS. 5, 6, 7 and 8) which is slidably receivable Within a complementary dovetail groove 38 formed in each of the aforesaid horizontal rail portions 18a and 20a. Also, in a manner similar to the shoulders 25 and 27 at the top of the backrest panel 26, the seat portion or panel 14 has a pair of shoulders 13 and (FIG. 4) marking the forward extremity of the flared dovetail edge 36 along each side, which shoulders abut the forward extremity of the rail portions 18a and a to limit the extent to which the seat portion 14 may be slid rearwardly upon the dovetail joint along each of its sides.

Beneath the seat portion 14 is located a support structure 40 (FIG. 4) which includes a pair of generally parallel bracing members 42 and 44 having end extremities 46 and 48, which, in effect, comprise elongated crossbars extending between members 42 and 44 at either end thereof. As shown in FIGS. 6 and 8, the bracing members 42 and 44 are spaced beneath the seat portion 14, whereas the top portion of the end extremity 46 (which is typical of either extremity 46 or 48) is formed to have a raised support shoe 50 having a slightly convex upper surface which bears against the bottom of the seat portion along an elongated area immediately adjacent the rail portion 18a and the dovetail joint of which Such rail portion is a part.

The edge of each of the cross-members or end extremities such as 46 has a generally V-shaped groove 52 (FIG. 5) formed therein, whereas the lateral inward face of each of the rail portions 18a and 20a has a complementary V-shaped protrusion or tongue 54 (FIG. 6) which fits into the groove 52 when the end extremities of the support structure are brought into abutment with the rail portions 18a and 20a, to thereby forrn a tongueand-groove joint 56 (FIG. 7). The V-shaped groove 52 defines a generally flat surface 58 (FIG. 8) which is inclined upwardly and outwardly with respect to the rail portion 18a, which surface mates with and rests upon a complementary surface 60 of the rail portion. Angle surface 58 of the support structure end extremity extends upwardly to communicate with the raised support shoe S0 formed atop `such end extremity to form a Wedge-like nose portion 62 which thus acts to clamp or wedge the edge extremity 63 of the seat portion immediately adjacent the flaring enlargement thereof which forms the dovetail 36 against an inwardly-directed lip 64 forming the top inward edge of the rail portion 18a. As illustrated in the drawings, the entire support structure 40, including the bracing members 42 and 44 and the cross-members 46 and 48 forming theend extremities of such bracing members and defining the support shoes 50, are all preferably formed integrally in a single casting.

As may be seen in FIGS. l, 3 and 5 through 8, the outer edge of the rail portion 18a (and also of rail portion 20a) has a longitudinally-extending groove 66 formed therein, which preferably extends over the entire length of rails 18 and 20. This provides an added design effect on the exposed portions of the rails, but more importantly, it serves astructural purpose on those portions which are not exposed. That is, the leg structures 22 and 24 seen in FIG. 4 include, in addition to the downwardly-extending legs themselves, a pair of inwardly-directed spaced attachment brackets 68 and 70 (FIGS. 4, 6 and 8). These extend laterally from the central portion of the U-shaped leg structures and iit beneath the end extremities 46 and 48 of the support structure 40, to which the attachment brackets are secured by machine screws 72 or the like. Located on the inward vertical face of the aforesaid central portion of the leg structures 22 and 24 is a projecting ridge 74 (FIGS. 6, 7 and 8). This ridge ts into the groove 66 in the outer surface of the rails in a tongue-andgroove arrangement when the attachment brackets 68 and 70 are secured to the end extremities of the support structure. As will be understood, this arrangement clamps the rail portions 18a and 20a between the leg structures and the end extremities of the support structure for an extremely strong and rigid construction. As indicated in FIG. 8, fillet-like reinforcement ribs 76 are preferably included in the chair leg structures 22 and 24, extending between the leg portions thereof and the attachment brackets 68 and 70.

The manner of assembling the present chair construction will likely already be apparent. As stated, the backrest panel 26 and the seat portion 14 are both assembled to the rails 18 and 20 by relative sliding of the dovetail joints present along the sides of each such member. When the seat portion and backrest panel are in the proper position, a desired number of lpins 78 such as are seen in FIG. 6 may be inserted through appropriate holes or passages to pin the dovetail joint between the seat p0rtion or backrest and the adjacent rail portions together,

, to prohibit any subsequent relative sliding of the dovetail joints and thereby hold the seat portion or backrest permanently in its assembled position. As will be understood, while pin 78 is illustrated as passing through the attachment bracket 68 of leg structure 24 as well as through the rail and flared enlargement forming the dovetail 36, a shorter pin may be used at any desired joint in excursion of either rail 18 or rail 20. With the aforesaid dovetail joints fully engaged in the desired manner, the support structure 40 is inserted into its proper position between rails 18 and 20, and the leg structures are then secured to the support structure with the rails located therebetween.

The construction on the present chair places the seat portion in a true sling suspension between the dovetail joints on either side thereof, in which the dovetail joints themselves sustain a major portion of the weight placed upon the seat portion by sitting thereupon, and in which the forces exerted on the seat portion in this manner are substantially completely tension forces. The presence of the support shoes alongside each of the dovetail joints supports the seat portion in this area and maintains a generally horizontal alignment thereof which keeps the seat portion in tension by eliminating or greatly reducing shear and bending stress concentrations.

It is entirely conceivable that upon examining the foregoing disclosure, those skilled in the art may devise particular embodiments of the concepts forming the basis of the invention which differ somewhat from the preferred embodiment shown and described herein, or may make various changes in structural details to the present embodiment. Consequently, it is to be recognized that the preferred embodiment shown and described is for purposes of general illustration only and is in no way intended to illustrate all possible forms of the invention.

We claim:

1. In a chair construction of the type having a seat portion and a frame including a rail portion disposed adjacent each of a pair of opposite edges of such seat portion, the improvement comprising: cooperative means along each of the opposite seat portion edges in said pair thereof and the rail portion adjacent each such edge forming a dovetail joint therebetween; said dovetail joint including an open-ended dovetail groove; said seat portion and said rail portions being interconnectable by engagement of said dovetail joint at said open end of said groove .and sliding said seat relative to said rail portions; and said joint arranged to sustain a major portion of the weight placed upon said seat portion by sitting thereupon to create a sling suspension of said seat portion *between said rail portions.

2. The improvement in chairs recited in claim 1, wherein sa-id seat portion has a flaring enlargement along each of its said opposite edges, and said open-ended dovetail groove is formed along each of said rail portions to slidably receive such seat portion enlargements.

3. The improvement in chairs recited in claim 2, further including a support structure having bracing means located beneath said seat portion and extending between said rail portions to maintain a predetermined separation between the latter.

4. The improvement in chairs recited in claim 3, wherein said support structure denes a generally rigid support shoe located in proximity to each of the opposite edges of said seat portion for supporting contact with the bottom of the latter generally adjacent said flaring enlargements along such edges.

5. The improvement in chairs recited in claim 4, Wherein said bracing means is spaced beneath sa-id seat prtion between said support shoes.

6. The improvement in chairs recited in claim 4, wherein said support structure bracing means has a pair of end extremities, each for abutting engagement with one of said rail portions.

7. The improvement in chairs recited in claim 6, wherein said support shoes are located atop said end extremities.

8. The improvement in chairs recited in claim 7, wherein said shoes are integrally formed with said end extremities.

9. The improvement in chairs recited in claim 8, wherein said bracing means is spaced beneath said seat Dortion between said support shoes.

10. The improvement in chairs recited in claim 6, wherein said abutting engagement of said bracing means end extremities and said rail portions comprises a tongueand-groove joint.

11. The improvement in chairs recited in claim 10, wherein said support shoes are located atop said end extremities.

12. The improvement in chairs recited in claim 6, wherein said end extremities each include a surface disposed at an angle extending upwardly and outwardly with respect to the rail portion in abutment therewith, and such rail portions each have a complementarily 'angled surface disposed beneath and in contact with the respective surface of the adjacent and abutting end extremity.

13. The improvement in chairs recited in claim 12, wherein said support shoes lare located atop said end extremities and said upwardly and outwardly angling surfaces of said end extremities each extend up to and cornmunicate With an edge of the respective support shoe.

14. The improvement in chairs recited in claim 12, wherein said abutting engagement of said bracing means end extremities and said rail portions comprises a tongueand-groove joint, and wherein said contacting angling surfaces of said end extremities and said rail portions each define a mating edge of such tongue-and-groove joint.

15. The improvement in chairs recited in cla-im 3, wherein said frame further includes chair leg structures having portions lying laterally along and outwardly of said rail portions, said leg structure portions secured to said bracing means to clamp said rail portions therebetween.

16. The improvement in chairs recited in claim 15, wherein said support structure defines a generally rigid support shoe located in proximity to each of the opposite edges of said seat portion for supporting contact with the bottom of the latter generally adjacent said ilaring enlargements along such edges.

17. The improvement in chairs recited in claim 16, wherein said support structure bracing means has a pair of end extremities, each for abutting engagement with one of said rail portions, and wherein said abutting engagement of said bracing means end extremities and said rail portions comprises a tongue-and-groove joint.

18. The improvement in chairs recited in claim 16, wherein said end extremities each include a surface disposed at an angle extending upwardly and outwardly with respect to the rail portion in abutment therewith, and such rail portions each have a complementarily angled surface disposed beneath and in contact with the respective surface of the adjacent and abutting end extremity.

19. The improvement in chairs recited in claim 18, wherein said abutting engagement of said bracing means end extremities and said rail portions comprises a tongueand-groove joint, and wherein said contacting angling surfaces of said end extremities and said rail portions each define a mating edge of such tongue-and-groove joint.

20. The improvement in chairs recited in claim 19, wherein sa-id bracing means is spaced beneath said seat portion between said support shoes.

21. The improvement in chairs recited in claim 20, wherein said support shoes are located atop said end extremities.

22. The improvement in chairs recited in claim 21, wherein said shoes are integrally formed with said end extremities.

23. The improvement in chairs recited in claim 22, wherein said leg structure portions and said rail portions include a mating tongue-and-groove structure.

24. In a chair construction of the type having a seat portion and a frame including a rail portion disposed adjacent each of a pair of opposite edges of such seat portion, the improvement comprising: cooperative means along each of said opposite seat portion edges and the rail portion adjacent each such edge forming a dovetail joint therebetween; said seat portion and said rail portions being interconnectable by relative sliding of said dovetail joint; a support structure disposed beneath said seat portion and having generally rigid support shoes located in proximity to each of the opposite edges of suchportion, for supporting contact with the bottom of the seat portion generally adjacent said dovetail joint; said joint arranged to sustain a major portion of the .weight placed upon said seat portion by sitting thereupon to create'a sling suspension of said seat portion between said'rail portions.

2S. In a chair construction of the type having a seat portion and a backrest portion, and also having a frame including a frame rail disposed adjacent each of a pair of opposite edges of at least one of said'portions, the improvement comprising: cooperative means along each of the said opposite edges of said portion and the said frame rail disposed adjacent thereto forming a dovetail jointtherebetween attaching such portion and rail together; said dovetail joint comprising a tongue structurehaving a portion of generally C-shaped cross sectional configuration intertting with a groove of complementary cross section, and further comprising a bracing ridge projection forming a part of said tongue structure and spaced at least slightly from said portion thereof interfitting with said groove, said means forming said joint providing support portions receiving said ridge projection in load-bearing relation.

26. The improvement in chairs recited in claim 25, wherein said bracing ridge projection is elongated and generally coextensive with said interfitting tongue portion.

27. The improvement in chairs recited in claim 25, wherein said tongue structure extends along the edges of said one portion, and said frame rails dene said groove and said support portions.

28. The improvement in chairs recited in claim 27, wherein said ridge projection extends angularly away from said one portion and is oriented toward the outside thereof, away from that surface of such portion contacting the body of a person sitting in the chair.

29. The improvement in chairs recited in claim 28, wherein said tongue structure and said one portion are integral with each other.

References Cited y UNITED STATES PATENTS 630,253 8/1899 Metting 297-460 3,041,110 6/1962 King et al. 297-451 3,124,390 3/1964 Eamset al. 297-458 3,253,860 5/1966 Shapiro 297-458 X 3,298,743 1/1967 Albinson et al. 297-445 3,300,251 1/ 1967 Helms 297-445 3,348,882 10/1967 Chassaignac 297-445 X CASMIR A. NUNBERG, Primary Examiner.

U.S. Cl. X.R. 297-458, 460 

